A Stone Age piece of chewing gum, one of the oldest discovered, has been found by an archaeology student in Finland.

The 5000-year-old glob still bears tooth impressions, was made from birch bark tar and looked "just like a dirty piece of modern chewing gum", Sarah Pickin told The Scotsman newspaper.

"I was also worried it could have been a bit of fossilised poo," she adds.

Pickin made the discovery while on a six-week volunteer program at the Kierikki Centre, an archaeological and exhibition site on the west coast of Finland.

The unflavoured birch bark contains carbolic acid, an antiseptic compound, which would have proved useful in treating mouth infections.

"By chewing this stuff, Neolithic people suffering from gum and throat infections might have found some relief," says Professor Trevor Brown, Pickin's tutor at the University of Derby.

The prehistoric chewing gum, which was used as a glue for fixing arrowheads to shafts, was made by simply heating birch bark.

"After the tar was made it was boiled and when it cooled it became solid. When it was heated again, it became softer, and it was used at least sometimes as some kind of chewing gum," says Sini Annala, an archaeologist at the Kierikki Centre.

A chewy history

Tar-like materials were chewed long before modern chewing gums were imported to Europe from the US in the last century.

The ancient Greeks chewed mastiche, a resin from the mastic tree, the Mayas used a natural gum from the sapodilla tree, while Native Americans munched on a resin cut from the black spruce tree.

Some of the oldest examples of black lumps of tar, complete with tooth marks, have been discovered in waterlogged bog sites in northern Europe, particularly Germany and Scandinavia. The earliest lump dates from the beginning of the Middle Stone Age.

Birch bark might have not tasted pleasant, though who knows what really captivated Neolithic taste buds.

Stress relief

But Brown believes it may have been chewed for enjoyment and as "merely a stress-relieving activity".

Whatever the purpose of chewing, the discovery is important for "the direct, graphical link with our ancestors", Brown says.

Pickin also found part of an amber ring and a slate arrow head. The items will go on display at the centre, along with the prehistoric chewing gum, once they return from laboratory analyses.